Alkylations of N4‐(4‐Pyridyl)‐3,5‐di(2‐pyridyl)‐1,2,4‐triazole: First Observation of Room‐Temperature Rearrangement of an N4‐Substituted Triazole to the N1 Analogue

Attempts to use alkylation to introduce a positive charge at the nitrogen atom of the 4‐pyridyl ring in the bis(bidentate) triazole ligand N⁴‐(4‐pyridyl)‐3,5‐di(2‐pyridyl)‐1,2,4‐triazole ( pydpt ) were made to ascertain what effect a strongly electron‐withdrawing group would have on the magnetic properties of any subsequent iron(II) complexes. Alkylation of pydpt under relatively mild conditions led in some cases to unexpected rearrangement products. Specifically, when benzyl bromide is used as the alkylating agent, and the reaction is carried out in refluxing acetonitrile, the N⁴ substituent moves to the N¹ position. However, when the same reaction is performed in dichloromethane at room temperature, the rearrangement does not occur and the desired product containing an alkylated N⁴ substituent is obtained. Heating a pure sample of N⁴‐Bzpydpt?Br to reflux in MeCN resulted in clean conversion to N1Bzpydpt.Br . This is consistent with N4‐Bzpydpt.Br being the kinetic product whereas N1Bzpydpt.Br is the thermodynamic product. When methyl iodide is used as the alkylating agent, the N⁴ to N¹ rearrangement occurs even at room temperature, and at reflux pydpt is doubly alkylated. The observation of the lowest reported temperatures for an N⁴ to N¹ rearrangement is due to this particular rearrangement involving nucleophilic aromatic substitution: a possible mechanism for this transformation is suggested.     

catena‐Poly[potassium [copper(II)‐μ‐isothiocyanato‐μ‐N‐salicylidene‐β‐alaninato(2–)]]

The title polymeric compound, catena‐poly­[dipotassium [bis­[μ‐N‐salicyl­idene‐β‐alaninato(2−)]‐κ⁴O,N,O′:O′′;κ⁴O′′:O,N,O′‐dicopper(II)]‐di‐μ‐iso­thio­cyanato‐κ²N:S;κ²S:N], {K[Cu(NCS)(C₁₀H₉NO₃)]}_n, consists of [iso­thio­cyanato(N‐salicyl­idene‐β‐alaninato)copper(II)]⁻ anions connected through the two three‐atom thio­cyanate (μ‐NCS) and the two anti,anti‐μ‐­carboxyl­ate bridges into infinite one‐dimensional polymeric anions, with coulombically interacting K⁺ counter‐ions with coordination number 7 constrained between the chains. The Cu^II atoms adopt a distorted tetragonal–bipyramidal coordination, with three donor atoms of the tridentate Schiff base and one N atom of the bridging μ‐NCS ligand in the basal plane. The first axial position is occupied by a thio­cyanate S atom of a symmetry‐related μ‐NCS ligand at an apical distance of 2.9770 (8) Å, and the second position is occupied by an O atom of a bridging carboxyl­ate group from an adjacent coordination unit at a distance of 2.639 (2) Å.     

A one‐dimensional zinc(II) coordination polymer incorporating [1,1′‐biphenyl]‐4,4′‐dicarboxylate and N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide ligands

In the title compound, catena‐poly[[[N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide]chloridozinc(II)]‐μ‐[1,1′‐biphenyl]‐4,4′‐dicarboxylato‐[[N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide]chloridozinc(II)]‐μ‐[N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide]], [Zn₂(C₁₄H₈O₄)Cl₂(C₂₆H₂₂N₄O₂)₃]_n, the Zn^II centre is four‐coordinate and approximately tetrahedral, bonding to one carboxylate O atom from a bidentate bridging dianionic [1,1′‐biphenyl]‐4,4′‐dicarboxylate ligand, to two pyridine N atoms from two N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide ligands and to one chloride ligand. The pyridyl ligands exhibit bidentate bridging and monodentate terminal coordination modes. The bidentate bridging pyridyl ligand and the bridging [1,1′‐biphenyl]‐4,4′‐dicarboxylate ligand both lie on special positions, with inversion centres at the mid‐points of their central C—C bonds. These bridging groups link the Zn^II centres into a one‐dimensional tape structure that propagates along the crystallographic b direction. The tapes are interlinked into a two‐dimensional layer in the ab plane through N—H...O hydrogen bonds between the monodentate ligands. In addition, the thermal stability and solid‐state photoluminescence properties of the title compound are reported.     

catena‐Poly[[[2,4‐dichloro‐6‐(pyridin‐2‐ylmethyl­iminomethyl)phenolato]copper(II)]‐μ‐thio­cyanato]

The title complex, [Cu(C₁₃H₉Cl₂N₂O)(NCS)]_n, is a novel thio­cyanate‐bridged polynuclear copper(II) compound. The Cu^II atom is five‐coordinated in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base ligand and one terminal N atom of a bridging thio­cyanate ligand defining the basal plane, and one terminal S atom of another bridging thio­cyanate ligand occupying the axial position. The [2,4‐dichloro‐6‐(pyridin‐2‐ylmethyl­imino­methyl)­phenolato]­copper(II) moieties are linked by the bridging thio­cyanate ligands, forming polymeric chains running along the a axis.     

2,5‐Disubstituted Pyrazolo[4,3‐c]cinnolin‐3‐ones

Complementary strategies to 2,5‐disubstituted pyrazolo[4,3‐c ]cinnolin‐3‐ones are reported herein, providing late stage substituent introduction at either the 2‐ or the 5‐position. Treating a readily prepared 4‐thiocinnoline ester with substituted hydrazines afforded late stage access to the 2‐position, while late stage substituent introduction at the 5‐position was achieved via two different strategies: alkylation of 4‐hydrazonopyrazol‐3‐ones, followed by a ring‐closing intramolecular S_NAr tactic and direct reaction of 5‐(2‐fluorophenyl)‐2,4‐dihydro‐3H‐pyrazol‐3‐ones with aryl diazonium salts, followed by cyclization. The strategies described herein provide practical and general methods to prepare 2,5‐disubstituted pyrazolo[4,3‐c ]cinnolin‐3‐ones.     

Photoluminescent and Liquid‐Crystalline Properties of Donor–Acceptor‐Type 2,5‐Diarylthiazoles

The synthesis of donor–acceptor‐type 2,5‐diarylthiazoles that bear electron‐donating N,N‐dialkylamine and electron‐withdrawing cyano groups at the 2‐ and 5‐position, respectively, were carried out with transition‐metal‐catalyzed C? H arylation reactions developed by us. The compounds were synthesized by the C? H arylation of unsubstituted thiazole at the 2‐position with a palladium/copper catalyst in the presence of tetrabutylammonium fluoride (TBAF) as an activator. Further C? H arylation of the 2‐arylated thiazole at the 5‐position was carried out by the palladium‐catalyzed reaction in the presence of silver(I) fluoride to afford the donor–acceptor‐type 2,5‐diarylthiazoles with N,N‐dialkylamine groups of different chain lengths. The UV/Vis absorption, photoluminescence, and electrochemical behavior were similar regardless of chain length, whereas liquid‐crystalline behavior and thermal characteristics were found to be dependent on the alkyl‐chain length. The compounds with N,N‐diethylamine or N‐butyl‐N‐methyl groups showed a stable liquid‐crystalline phase over a wide temperature range as well as higher stability to thermal decomposition.     

Ethyl 1,4‐Dihydro‐4‐oxo‐1,8‐naphthyridine‐3‐carboxylates by a Tandem SNAr‐Addition‐Elimination Reaction

A series of N‐substituted 1,4‐dihydro‐4‐oxo‐1,8‐naphthyridine‐3‐carboxylate esters has been prepared in two steps from ethyl 2‐(2‐chloronicotinoyl)acetate. Treatment of the β‐ketoester with N,N‐dimethylformamide dimethyl acetal in N,N‐dimethylformamide (DMF) gave a 95% yield of the 2‐dimethylaminomethylene derivative. Subsequent reaction of this β‐enaminone with primary amines in DMF at 120^oC for 24 h then afforded the target compounds in 47–82% yields by a tandem S_NAr‐addition‐elimination reaction. Synthetic and procedural details as well as a mechanistic rationale are presented.     

Synthesis and tuberculostatic activity of novel N′‐methyl‐4‐(pyrrolidin‐1‐yl)picolinohydrazide and N′‐methylpyrimidine‐2‐carbohydrazide derivatives

The synthesis of N′‐methyl‐4‐(pyrrolidin‐1‐yl)picolinohydrazide and N′‐methyl‐pyrimidine‐2‐carbohydrazide derivatives ( 5a and 5b ) was carried out. These compounds were used as starting materials to obtain methyl N′‐methylhydrazinecarbodithioates 6a and 6b , which, on reaction with either triethylamine or hydrazine, gave corresponding 1,3,4‐oxadiazioles 7a and 7b or 1,2,4‐triazoles 9a and 9b with the free NH₂ group at the N‐4 position, respectively. Compounds 8a – e , particularly containing cyclic amines at N‐4 of the 1,2,4‐triazole ring, were also obtained. Synthesized compounds were tested in vitro for their activity against Mycobacterium tuberculosis. The structure–activity relationship analysis for obtained compounds was done. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:223–230, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21008     

[Di‐2‐pyridyl ketone N4,N4‐(butane‐1,4‐di­yl)­thio­semi­carbazonato‐κ3N,N′,S]­di­oxo­vanadium(V)

The V^V atom in the title complex, [V(C₁₆H₁₆N₅S)O₂], is five‐coordinate in a highly distorted square‐pyramidal geometry, with the pyridyl N, the azomethine N and the thiol­ate S atoms of the di‐2‐pyridyl ketone N⁴,N⁴‐(butane‐1,4‐di­yl)­thio­semi­carbazone ligand and one oxo ligand occupying the basal coordination positions, while the second oxo ligand occupies the apical position. The mol­ecules are inter­connected by weak inter­molecular inter­actions, mainly of the C—H⋯O type, involving the oxo atoms.     

Multiple intramolecular hydrogen bonds in 2,4‐di‐tert‐butyl‐6‐[N‐(2,6‐diisopropylphenyl)‐P,P‐diphenylphosphorimidoyl]phenol

The title compound, C₃₈H₄₈NOP, isolated from the reaction of (2‐diphenylphosphanyl‐4,6‐di‐tert‐butyl)phenol with 2,6‐diisopropylphenyl azide at 273 K, can act as an N,O‐bidentate ligand. Crystal structure analysis shows a deviation from ideal tetrahedral symmetry around the P atom. The molecule exists as a monomer in the solid state, whose conformation is stabilized via multiple intramolecular hydrogen bonds. Geometric parameters from both experimental and theoretical calculations are compared.     

Di‐μ‐aqua‐bis­[(N‐salicyl­idene‐β‐alaninato‐κ3O,N,O′)copper(II)] urea disolvate

Crystals of the title compound, [Cu₂(C₁₀H₉NO₃)₂(H₂O)₂]·2CH₄N₂O, consist of two (N‐salicyl­idene‐β‐alaninato‐κ³O,N,O′)copper(II) coordination units bridged by two water moieties to form a dimer residing on a crystallographic inversion center, along with two uncoordinated urea mol­ecules. The Cu^II atom has square‐pyramidal coordination, with three donor atoms of the tridentate Schiff base and an O atom of the bridging aqua ligand in the basal plane. The axial position is occupied by the second bridging water ligand at a distance of 2.5941 (18) Å. Hydro­gen bonds between mol­ecules of urea and the neighboring dimer units lead to the formation of a two‐dimensional grid of mol­ecules parallel to [101]. The superposition of the normals of the pyramidal base planes in the direction [100] indicates possible π–π interactions between the neighboring units.     

One‐Pot Four‐Component Synthesis of N2‐Alkyl‐N3‐[2‐(1,3,4‐oxadiazol‐2‐yl)aryl]benzofuran‐2,3‐diamines

A simple synthesis of N²‐alkyl‐N³‐[2‐(1,3,4‐oxadiazol‐2‐yl)aryl]benzofuran‐2,3‐diamines 5 via a one‐pot four‐component reaction is described (Scheme 1). A mixture of N‐(isocyanoimino)triphenylphosphorane ( 1 ), a 2‐aminobenzoic acid 2 , a 2‐hydroxybenzaldehyde 3 , and an isocyanide 4 in absolute EtOH at room temperature undergoes a smooth reaction to afford 5 in excellent yields (Table).     

Hydrogen‐bonded supramolecule of N,N′‐bis(4‐pyridylmethyl)oxalamide and a zigzag chain structure of catena‐poly[[[dichloridocobalt(II)]‐μ‐N,N′‐bis(4‐pyridylmethyl)oxalamide‐κ2N4:N4′] hemihydrate]

N,N′‐Bis(4‐pyridylmethyl)oxalamide, C₁₄H₁₄N₄O₂, exists as a dimer which is extended into a two‐dimensional network with other dimers through pyridine–amide hydrogen bonds. The crystal structure of the title coordination polymer, {[CoCl₂(C₁₄H₁₄N₄O₂)]·0.5H₂O}_n, features a one‐dimensional zigzag chain, in which the cobalt ion sits at a twofold symmetry position and adopts a tetrahedral geometry, and the bridging ligand lies on an inversion center and connects to Co^II ions in a bis‐monodentate mode. Furthermore, two interwoven chains create a cavity of ca 8.6 × 8.6 Å, which produces a three‐dimensional channel. Water molecules are held in the channel by hydrogen bonds.     

Dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate and bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ2N,N′)copper(I) tetrafluoroborate

The single‐crystal X‐ray structures of dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate, C₁₄H₁₂N₂O₄, and the copper(I) coordination complex bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ²N,N′)copper(I) tetrafluoroborate, [Cu(C₁₄H₁₂N₂O₄)₂]BF₄, are reported. The uncoordinated ligand crystallizes across an inversion centre and adopts the anticipated anti pyridyl arrangement with coplanar pyridyl rings. In contrast, upon coordination of copper(I), the ligand adopts an arrangement of pyridyl donors facilitating chelating metal coordination and an increased inter‐pyridyl twisting within each ligand. The distortion of each ligand contrasts with comparable copper(I) complexes of unfunctionalized 2,2′‐bipyridine.     

Synthese und Struktur von N,N,N‴,N‴‐Tetraisobutyl‐N′,N″‐isophthaloylbis(thioharnstoff) und Dimethanol‐bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))dicobalt(II)

Synthesis and Structure of N,N,N?,N?‐Tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and Dimethanol‐bis(N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))dicobalt(II) The synthesis and the crystal structure of the ligand N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and its Co^II‐complex are reported. The ligand co‐ordinates quadridentately forming a di‐bischelate. The donor atoms O and S are arranged in cis‐position around the central Co^II ions. In addition the co‐ordination geometry is determined by methanol molecules resulting in the co‐ordination number five. The complex crystallizes in the space group P1 (Z = 1) with two additional methanol molecules per formula unit. The free ligand crystallizes in the space group P1 (Z = 2) with one methanol molecule per formula unit. It shows the typical keto form of N‐acylthioureas with a protonated central N atom. The structures of both acylthiourea fragments come close to E,Z′‐configurations.     

Solvent‐ and Temperature‐Controlled In Situ Ligand Reactions Mediated by CuII and 3′‐[(E)‐{[(1S,2S)‐2‐Aminocyclohexyl]imino}methyl]‐4′‐hydroxy‐4‐biphenylcarboxlic Acid

Three new compounds, CuL, CuL′, and Cu₂O₂L′′₂ (H₂L=3′‐[(E)‐{[(1S,2S)‐2‐aminocyclohexyl]imino}methyl]‐4′‐hydroxy‐4‐biphenylcarboxlic acid, H₂L′=3′‐[(E)‐{[(1S,2S)‐2‐aminocyclohexyl]imino}methyl]‐4′‐hydroxy‐5′‐nitro‐4‐biphenylcarboxlic acid, H₂L′′=3′‐(N,N‐dimethylamino methyl)‐4′‐hydroxy‐4‐biphenylcarboxlic acid), were selectively synthesized through a controlled in situ ligand reaction system mediated by copper(II) nitrate and H₂L. Selective nitration was achieved by using different solvent mixtures under relatively mild conditions, and an interesting and economical reductive amination system in DMF/EtOH/H₂O was also found. All crystal structures were determined by single‐crystal X‐ray diffraction analysis. Both CuL and CuL′ display chiral 1D chain structures, whereas Cu₂O₂L′′₂ possesses a structure with 13×16 Å channels and a free volume of 41.4 %. The possible mechanisms involved in this in situ ligand‐controlled reaction system are discussed in detail.     

Chloro(η6‐p‐cymene)(2‐methyl‐5‐oxo‐7‐phenyl‐5,6‐di­hydro‐2H‐1,2,4‐triaz­epine‐3‐thiol­ato‐κ2N4,S)­ruthenium(II)

The novel title ruthenium(II) complex, [RuCl(C₁₀H₁₄)(C₁₀H₁₀N₃OS)], was synthesized from the reaction of 1,2,4‐triazepine, a new class of bidentate ligands, with [Ru(p‐cymene)Cl₂]₂. The 1,2,4‐triazepine ligand is coordinated to the metal centre through the N‐4 and S atoms, forming a four‐membered chelate ring. This is the first structural example of a transition metal complex containing a 1,2,4‐triazepine ligand.     

(2,2′‐Dipyridyl sulfide‐N,N′)hydroxybis(nitrito‐O)(nitrogen monoxide‐N)ruthenium(III)

The title compound, [Ru(NO₂)₂(OH)(C₁₀H₈N₂S)(NO)], is the main product of the reaction between RuCl₃ and dps (dps is 2,2′‐dipyridyl sulfide, C₁₀H₈N₂S) in ethanol–water at room temperature followed by reaction with NaNO₂ at a higher temperature. The Ru atom has a distorted octahedral coordination geometry with the dps mol­ecule behaving as an N,N′‐bidentate ligand. The six‐membered chelate ring adopts a boat conformation.     

Synthesis and characterization of a cadmium(II)–organic supramolecular coordination compound based on the multifunctional 2‐amino‐5‐sulfobenzoic acid ligand

Much attention has been paid by chemists to the construction of supramolecular coordination compounds based on the multifunctional ligand 5‐sulfosalicylic acid (H₃SSA) due to the structural and biological interest of these compounds. However, no coordination compounds have been reported for the multifunctional amino‐substituted sulfobenzoate ligand 2‐amino‐5‐sulfobenzoic acid (H₂asba). We expected that H₂asba could be a suitable building block for the assembly of supramolecular networks due to its interesting structural characteristics. The reaction of cadmium(II) nitrate with H₂asba in the presence of the auxiliary flexible dipyridylamide ligand N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide (4bpme) under ambient conditions formed a new mixed‐ligand coordination compound, namely bis(3‐amino‐4‐carboxybenzenesulfonato‐κO¹)diaquabis{N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide‐κN}cadmium(II)–N,N′‐bis[(pyridin‐4‐yl)methyl]oxamide–water (1/1/4), [Cd(C₇H₆NO₅S)₂(C₁₄H₁₄N₄O₂)₂(H₂O)₂]·C₁₄H₁₄N₄O₂·4H₂O, (1), which was characterized by single‐crystal and powder X‐ray diffraction analysis (PXRD), FT–IR spectroscopy, thermogravimetric analysis (TG), and UV–Vis and photoluminescence spectroscopic analyses in the solid state. The central Cd^II atom in (1) occupies a special position on a centre of inversion and exhibits a slightly distorted octahedral geometry, being coordinated by two N atoms from two monodentate 4bpme ligands, four O atoms from two monodentate 4‐amino‐3‐carboxybenzenesulfonate (Hasba⁻) ligands and two coordinated water molecules. Interestingly, complex (1) further extends into a threefold polycatenated 0D→2D (0D is zero‐dimensional and 2D is two‐dimensional) interpenetrated supramolecular two‐dimensional (4,4) layer through intermolecular hydrogen bonding. The interlayer hydrogen bonding further links adjacent threefold polycatenated two‐dimensional layers into a three‐dimensional network. The optical properties of complex (1) indicate that it may be used as a potential indirect band gap semiconductor material. Complex (1) exhibits an irreversible dehydration–rehydration behaviour. The fluorescence properties have also been investigated in the solid state at room temperature.     

catena‐Poly­[[di‐μ‐benzoato‐κ4O:O′‐disilver(I)]‐μ‐N,N′‐bis(2‐fluoro­benzyl­idene)­butane‐1,4‐di­amine‐κ2N:N′]

The title complex, [Ag₂(C₇H₅O₂)₂(C₁₈H₁₈F₂N₂)]_n, is a dinuclear silver(I) compound with one inversion centre between pairs of Ag atoms and another at the mid‐point of the central C—C bond in the butane‐1,4‐diamine moiety. Each of the smallest repeat units consists of two silver(I) cations, two benzoate anions and one N,N′‐bis(2‐fluorobenzyl­idene)­butane‐1,4‐di­amine Schiff base ligand. Each Ag^I ion is three‐coordinated in a trigonal configuration by two O atoms from two benzoate anions and one N atom from a Schiff base ligand. The di‐μ‐benzoato‐disilver(I) moieties are linked by the bridging Schiff base ligand, giving zigzag polymeric chains with an [–Ag⋯Ag—N—C—C—C—C—N–]_n backbone running along the b axis.